Effect of home-based transcranial direct current stimulation (tDCS) on cognitive functioning in bipolar depression

Bipolar depression is commonly accompanied by cognitive impairments. Transcranial direct current stimulation (tDCS) is emerging as a novel non-invasive treatment for bipolar depression. Given the portability and safety of tDCS, we developed a home-based protocol with real-time supervision. Our aim was to assess the cognitive effects of tDCS in bipolar disorder. 44 participants (31 women, mean age 47.27 ± 12.89 years) experiencing a moderate to severe depressive episode received 21 sessions of home-based tDCS over 6 weeks. The stimulation protocol involved 2 mA in a bilateral frontal montage (F3 anode, F4 cathode) for 30 minutes per session. The cognitive assessments were conducted at baseline and after the course of treatment. Rey Auditory Verbal Learning Test (RAVLT) was used to assess verbal learning and memory and the Symbol Digit Modalities Test (SDMT) to assess psychomotor processing speed and visuospatial attention. 93.18% (n=41) completed RAVLT and 59.09% of participants (n=26) completed SDMT. A significant improvement was observed in the RAVLT short-term verbal memory score post-treatment (p = 0.002). Improvements were observed in RAVLT verbal learning, RAVLT post-interference recall, and SDMT, which were not statistically significant. In summary, cognitive performance showed an improvement in bipolar depression following treatment with home-based tDCS, suggesting it can be an effective intervention for cognitive deficits in bipolar depression and positively impact cognitive function.